Method of treating wells



Flpi flfi I g rls-ed States Patent 3,286,770 g Marriott OF TREATING WELLS John A.

assignors to Halliburton Company, Duncan, Okla, a corporation of Delaware 1 No Drawing. Fiied h'lay 25, 1965, Ser. No; 458,772

- v Claims. (Cl. 166--42).

This application. is a contin uation-i n-part of US. patent application Serial No; 140,190, now abandoned, filed Sep temberZS 1961, which is a continuation-impart of US.

patent application Serial' No; 40515, filed July 5, 19 60,

now abandoned, and is entitled to all the benefits and rights of said earlier filed applications as-to all common subject: matter. I

This invention relates generally to the treating of wells and, more particularly, to compositions and methods use- V ful in treating undergrou'nd well structures to render surfacesv thereof water-repellent or preferentially oil-wettable.

It is anticipated thatthe invention: will be most widely applied in connection with operations performed on disposal and injection wells wherein water or other aqueous Knox and Reginald M. Lasater, Duncan. Okla I through which water 3,286,770 Patented Nov .122, 1966- pellent the surfaces of a permeable structure therein, such as surfaces of rock or sand zone'or formation into and is conducted during the course of operating the well. I a

Yet a further object of the present invention is to provide a new and improved treating agent for water injection, water disposal wells, and/orwater wells consisting essentially of an organohalogensilane or ester thereof, 'or' mixtures of either or both, and a water soluble solvent which is substantially non-reactive or inert with the organo silane compound.

Yet a furtherobiect of the present invention is toprovide a new and improved method of treating water injection, water disposal wells, and/or waterwells, whereby an organohalogensilane compound, which does not form a precipitate upon hydrolysis with water, is used"""' to render the. well formation substantially permanentlypreferentially oil-\vettable.

fluidv is to be injected into the treated zone or forrnation. In these and other instances it has been found desirable for the surfaces past which the aqueous fluid is conducted to bewater repellent in order to facilitate or increase the'fluid movement, such as into and through the pore spaces and openings providing fluid passageways in thetreated zone for formation, which is commonly a permeable rock or sand structure.

While various proposals have been made heretofore to render surfaces in wells preferentially oil-wet, these have commonly provided only temporary water repellency, such as by using surface active or wetting agents which. become adsorbed on surfaces of the permeable structure to be treated'but which do not actually react chemically therewith. In some instances the effect of these agents has been lost-due to the agent being washed away relativelyrapidly when water or other aqueous fluid is subsequently flowed or conducted therepast. At times the prior art agents have been introduced into wclls in oily carrying fluids which are difficult to use advantageously in water wells, due to remaining in' the well and forming plugging or blocking deposits. For example, emulsification has occurred between the oil present in the carrying fluid I and water present or introduced into the well.

This emulsification may occur, for example, when water is subsequently introduced during the course. of operating a Water disposal or injection well.

One object of'the present invention is to provide an 7 improved treating went and an improved method using the same in rendering surfaces water-repellent or preferentially oil-wettable. 7

Another object of the invention is to pro ide an im proved treating agent and method useful in rendering surfaces water-repellent or preferentially oil-wettable for much longer periods of time than with certain prior art practices.-

Ahcth'er and more specific object of the invention is to provide an'improved-treatirig agent and method for use in rendering the surfaces of a rock or sand structure water-repellent or preferentially oil-wettable.

Another specific object of the invention is to provide an improved treating agent and method for use in well operations wherein it is desired to render the surfaces of a permeable zone or formation in the well water-repellent or preferentially oil-wettable, such 'as to facilitate the movement of water or other aqueous fluid therepast.

A further specificobject of the invention is to provide an improved treating agent and method especially useful in halogensilanes, e.g., amyltrichlorosilane, ethylltrichloro- The foregoing and additional obje cts and advantages are attained, in accordance with the invention, by utilizing a treating fiuiri comprising a treating'agent and a carrier therefor, wherein a liquid organoh'alogensilane or ester thereof, which does not form a precipitate upon hydrolysis with water, is the treating agent anda water soluble anhydrous solvent which is substantially inert or not reactive with the silane is the carrier.

The present invention is' specifically adapted for treat ing formations having no oil present, and one in which no oil is to subscquently come in contact therewith. The

formation to be treated should bewater wet, and if the formation is n'ot'water wet, it shouldbe rendered water-i 1- f wet prior to carrying out the treating method of this,

invention.-

The organhalogensilzmes or esters thereof suitable for use in the instant invention are those which do not form a precipitate upon hydrolysis with water. Some examples of suitable organohalogensilane compounds are the alkylsilane, methyltrichlorosilane, trirnethylchlorosilane, di-. methyldiehlorosilane, methyltribromosila'ne, dimethyldibromosilane 'and trirnethylbromosilane; the alkenylhalogensilanes, e.g., vinyltrichlorosilahe; the arylhalogensilanes, e.g.,' diphenyldichlorosilanes, phenyltrichlorosilane, and diphenyldibromosilane; the ailq lorganosilane esters, e.g., amyltriethoxysilane, ethyltriethoxysilane, methyltriethoxysilane, and dimet'hyldiethoxysilane; the alkenylorganosi-lane esters, e.g., vinyltriethoxysilane; and the aryl-v organosilane esters, e.g.,diphenyldiethoxysilane and phenyltriethoxysilane.

It should be noted that mixtures'of the above organohalogensilanes and/or esters thereof may be used without departing from the scope of the invention. Generally, the. organohalogensilanes are preferred over the A drolysis and the esters of such organohalogensilancs watcrdisposal or injection wells for rendering \vater-reesters ihereof because of their faster reaction in hydrolyzingl There are of course some situations in which it would be more desirable to have a slower rate of hywould therefore be preferred. The chlorosilanes are-generally preferable, because of their more readily commer v R -Si-X v wherein R may bean alkyl, alkcnyl or aryl group having from 1 to 18 carbon atoms; n may be from 1 to 3, n

their halogen.

- The esters of the organobalogensilanes most suitable for use in the invcntionare those hailing the general for mula R .-Si(OR') wherein R and R. may be an alkyl, alkenyl or aryl group having from 1 to 18 carbon and n+n' equal 4; O is oxygen and .(OR) may be a hydrogen, but the ester must have at least one OR group..

R may also be an OR group,

, The organoha-logensilane of the present invention as 'set forth hereinabove is dissolved in a water soluble anhydrous solvent or' carrier: which carrier is substantially Suitable carriers or solvents are alcohols, e.g., isopropyl I alcohol, ethyl alcohol and metbylalcohol; ketones, .e.g.,-

acetone, andmethyl ethyl ketone; amides, e g. formamide; and anhydrous organic acids, e.g.', glacialacetic acid,

maybe from 110 3, and Il -Err equalsfi; and'X may be a hydrogenor halogen, but silane must have at least one atoms; :2 may be from 1 to 3; 11' may be from 1 to 3,

1 ing fluid from water and other contaminating substances which may be encountered in the w'ell.

formic acid and acetic anhydride Any other suitable water, soluble, anhydrous solvent which is'subs'tantially hon-reactive with the organohalogensilanes or esters there ofmaybeused. I

As stated hereinabove, when a surfactant is used as a treating fluid such surfactant is adsorbed on the surface of the sand or formation and there is a very weak attachment or bonding as compared to that which'occurs in a chemical reaction. The energy which holds the surfactant plugs or the like may be introduced and moved or forced on the solid surface of the formation is usually less than t 10 kilocalories/ mole. This means that the surfactant may be easily removed by washing with a solvent.

in the case of the well treating fluid of thepresent inention, there is art-actual chemical reaction of the siiane material with the surface of the sand or formation. which The following illustrates the reaction 'of an organohalogensilane with silica surfaces or sand;

(a) If the silica has a layer of water on the surface there are two reactions which occur 7 (b) If the silica surface is free of water then the reactionis 4 ll, v l\- v In the first equation the sand reacts 'with the silane to form a silanol and water. The silanol hydrolyzes, as seen in Equation 2, to form the sand or silicapolymer which creates the chemical bond and water. In Equation firmly attaches such'material to the sand- This bond er'rergy' is. on the order of 100 kiloealories/mole, thereby allowing a nearly permanent attachment.

- the bonding polymer and an acid. I WaYd p oceeding in the present invention, f

into'a water disposal or injection well, quantities ofthe packer arrangements may be employed, it is preferred to a ditferentfsection. This type of tool is well known in. f the oil fields and, accordingly, it is believed unnecessary 3, the silane reacts directly with-the silarrol group to form the treating fluid is prepared by dissolving a quantity of amyl trichlorosilan'ein a suitable solvent, such as isopropylalcohol or acetone.v

While the invention is not limited to any particular theory of behavior of the ingredients, it is believed that the sol'vent-silane.system.should be kept as free of water as possible until his introduced into the well and reaches thezone or formation to be treated. This precaution is to prevent premature hydrolysis of the silane material.

In introducing the t'reatinglluid into a well, such. as

sol ent alone or some other suitable fluid may advantageou'sly be introduced as a blanketing or flushing fluid. V The blanl eting fluid may be used ahead of and behind the solvent-silane solution'to assist in isolating the treat- The blanketing or flushing fluid used as a spear-head or i tail-in removes and displaces any interstitial water, but permits a film of water to be retained Orr-the sand. This blanket enables-the silane' to. be properly placed without. I adverse efl'ects such as a premature reaction of the silane' with' interstitial water.

If desired, one or more separators in theform of well downwardly into the well. For example, the treating fluid and perhaps also the blanketing fluid may be introduced between top and bottom plugs which eventually come to rest in the well. The top plug may be followed by a quan 4 tity of a displacing fluid, which may be water pumped into the well tubing or other conduit to move 'or force the plugs and treating fluid downwardly into the well. v

In order to isolate the treating fluid and facilitate itsinjection, well packers may be employed at one or both locations above and below the section of well strata to be treated. Where there is a zone or formation of considerable vertical dimension, best results will be obtained by-v Q treating relatively short sections thereof while. isolated by well packers or the like. While any of various straddle use a combination tool which provides relatively close, spacing of the top and bottom packers and permits ready movement of thewhole tool when it is desired to treat to give a full description herein.-

If desired, the treating fluid can be spotted at the dc.- sired depth in" the well and then slowly squeezed into the zoneor formation or section thereof to be treated-c Where this procedure is. followed, it is recommended that care be. taken to avoid premature overdisplacement of the treating fl'uid into the well strata. More particularly, it is recommended that the treating fluid, after introduction thereof into the well strata, be allowed tor'emain relatively near the bore-of the well for a suflicient period of time to allow the silane material to reach and react with as much as possible. of the exposed'o'r accessible sand and like sub stances in the section to be treated.

To this end, the well may advantageouslybe closed in for several hours or the treating fluid may otherwise be 5 or iemoving the excess fluid. In any event,'where the 2 Well is a water disposal or injection well, it is recommended that a delay occur following the. treatment and 4 prior to commencing or resuming the injection of water or otherwise operating the welL It is believed unnecessary to attempt to recover thetreating fluid from the vwell, particularly where water or 3 other aqueous fluid is to be injected into the treated zoneor formation after the treatment thereof. '5 The amount of treating fluid to be used in any particular well will, of course, depend upon several factors.

i l l i i X hours.

T fFor best resutls, it is believed that some attempt should be I made to estamiate or measure the dimensions of the zone or formation to be treated; whereupon an estimate can be made as to the amount of treating agent or silane likely to be required. v

For example, itis believed that 1 gram molecular weight of the s'ilane material will cover approximately 1,100 square meters surface area.

lt-is estimated that a section of well formation one feet thick and two feet in diameter will have a surface area of about 34,000 square meters,

- assuming36 percent porosityand 100 millidarcies permeallowed to pass through'the sand under gravity flow conditions, with the time required'for thequantity between 10 cc. and cc. passing through-the pack being measured. Aseach sand pack was prepared, it was similarly tested.

After preparing the sand packs,.'each was then suppliedwith cc. of water which was placed on top of the sand. 'A pressure line was connected to the top of the flow col-. umn. The pressure was adjusted by means of a pressure regulator and mercury manometer to a pressure differential of 5.2j'cm. of mercury which is approximately equal to 1 psi. The flow rate of the water through the sand pack .ability. In this instance, it is believed that approximately 6,750 grams or 15 pounds of amyl tri'chlorosilan'e would be needed for full treatment; This amount of treating agent could be mixed with an amount of solvent (about 7gallons) estimated to equal the pore volume of the section to be'treated; The resulting treating fluid could then be applied,'as aforesaid, byintrod'ucing it between blanketi ng fluids. Alternatively, the treating fluid could be in jectedinto the well strata using any of various equivalent procedures, suchas by lowering it in a dump bailer or otherwise employing suitable tools for placing the fluid at the desired location in the well.-

Concentrations (wt. percent) of silane solution used will vary depending on the particular silane' used. This is determined by .the number of gram-moles required to treat the exposed rock.. The above sample shows 32.9

gramanoles is necded (15 lbs.) of amyl trichlorosilane tot're at the given formation. When dissolved in enough solvent to fill the pore spaces this gives a 30.4% 'by weight solution. Following the same procedure for trimethyl chlorosilane gives 16.5% and for diphenyldiethoxy silane, 35.2%. It is not possible to determine, with any degree of certainty, how much dilution is obtained with water in the formation- There should be very little, however,

because the bulk of the water will be displaced ahead of the treating solution. Itis believed that not more than "about 30% of the water will be retained and this. would dilute a 33% solution of siiane to about 30% by weight; The concentrations shown hereiriabove are based on the condition that the zone in question is to be entirely treated with silane with one pore, volume of fluid. .The concern.

'trations can: be reduced by using more than one pore volume. Thus, concentration limits can be from 1% .to

: byweight with the preferred range being 15-35%.

Laboratory tests have been conducted for the purpose of comparing the flow rate of water through untreated sand packs with the flow rate of water through otherwise.

similar sand packs which had been first treated, in accordance with the invention,'to render the surfaces thereof water-repellent or preferentially oil-wettable. Also,

measurement was made of the flow rate of kerosene through the treated and untreated sand packs after water had passed therethrough. Subsequently, measurement was made of the how rate of additional water which was passed through the sand packs after the kerosene; in order to compare the efi'ect'of the kerosene on the treated and untreated sand packs.

In preparing for these tests a quantity of Oklahoma #1 dry sand was first treated, in accordance with the inverition, using a 0.2 percent byweight solution of diethyl diethoxy silane in acetone. The sand was covered with was then measured and. recorded. The tests were repeated using additional water. Then the tests were repeated on both sand packs using kerosene instead ofwater. The tests were repeated on the sand packs using water and finally with water once again. Theresults of these tests are shown in Table I.

TABLE I [Flow rates through column (ea/reel] Untreated Sand Dlethyl Dlethoxy Test Fluid Pack Silane Treated I Sand Peck It can readily be seen that water passes more freely through the treated, sand packthan through the untreated sand pack. Upon the basis of these results and others, it is believed that the ,fiowmte of water through treated sand can be expected to average about 26 percent greater than through similar sand which has not been treated to V make it water-repellent or preferentially oil-.wettable.

With regard to the tests first using water, it is emphasizedthat the treated sand is not oil-wet in the sense of being in contact with oil. That'is, no oil is'actually in I Rather, the sand is contact with the treated sand.

coatedl with a silicone type material which renders the surf-aces water-repellent and preferentially oil-wettable.

0n the other hand,'in the test usingwater after having I previously used kerosene, the treated sand pack has now 'become oil-wet, whereas the untreated sand pack-is still preferentially water-wet, which is the usual condition of untreated sand surfaces. While in. such test the untreated ,sand packcontains residual 'oil,- due to having been in contact with the kerosene of the prior test, the oilwvet treated sand pack contains excess oil'contamination, which explains the lower water flow rates the'rethrough in these subsequent water tests.

In this latter connection, however, it is pointed out that the contamination of the treated sand with oil can be remedied. That is, it is possible to wash theoihwet sand with water containing soap or a surfactant and thereby.

remove the excess oil. However, the introduction of oil into treated formations is to be'avoided where maximum benefits from the treatment are desired.

In additional tests, the oil wetting of sandby diethyl diethpxy, amyl triethoxy, and amyl trichloro silane was determined visually. The flow of water through amyl the treating solution, agitated slightly, and then allowed to remain in contact with the solution for approximately 1 hour. Next, theexcess liquid was decanted and the sand was dried at 110 degrees centigrade for approximately 16 independent tests showed that sand treated in this manner is very preferentially oil-wettable. The treated sand, after drying, and a quantity of otherwise similar but untreated, dry sand were usedin prepar- -"-*-ing the treated and untreated sand packs.

In preparing each of the sand packs, 40 cc. of sand was added to a glass tube. The sand pack was then tested in an attempt to determine the uniformity of packing of the sand. This was done by adding 50. cc. of water which was triethoxy silane treated sand was measured and compared 7 with that of the other two silanes. These results are set as follows:

phase at the end of the test with one exception. Dimethyl 7 WWW Thus, it appears that'the water flow rate is dependent upon the degree of oil wetting afforded by the'silane. The

increase in flow rate above that of the water' wet sand is Percent The results of the tests also show that the'flow rate of oil through water wet sand is greater than through all wet 0.

' Solutions of the'silane esters (obtained from- Union Carbide, Siliconcs Division) werepreparcd in acetone 9 using 3 cc.- of silane and 10 g. acetone (33% solution).

Two cubic centimeters of solution were added to bottles containing 50 cc. water'and capped. The bottles .were H allowed'to stand for 24 hours with. occasional shaking. The results are as follows: 1

- Results Appearance after Chemical: .7 .24hours A-lS ethyl tri'ethoxy silane Clear solution, oil on top, no solids.

' A46 amyl triethoxy silane--- Clear solution, oil on top, no solids.

A-151 vinyl triethoxy silane So In t ion slightly e g t U cloudy, oil on top,

no evidence of solids.

A-153 phenyl triethox-y silane- Clear solution, oil on l I top, no solids. A-l64 dimethyl diethoxy s il- 4Q ane' Solution clear, no oil layer detected.

The glass containers were water repellent at the end of the tests with A464 being the most water repellent.

Conclusions Hydrolysis of ethyl triet hoxy silane, amyl triethoxy silane, vinyl triethox'y silane, phenyl triethoxy silane, and

dimethyl diethoity silane in water for 24 hours did not produce evidence of solids precipitating. Themixtures 50 of silane and water had an oily layer 'on top of the aqueous dietho'xy silane upon hydrolysis apparently forms a water soluble product as there was no oily layer present.

TABLE IV v Procedure The silane esters were purchased from Peninsular Chemresearcl't Company. Solutions'were prepared by dis-, solving 3 cc. of silane in 10 g. acetone (33% solution). 0 Two cubic centimeters of solution were added to flasks containing 50 cc. water and the flasks stoppered. The flasks were allowed to stand for 24 hours with occasional shaking. 7

All glass containers were used in these tests. r 5 Results Appearance after Chemical: 24 hours Trimethyl-ethoxy silane.... Oil layer on top of water, no solids. Diethyl dicthoxy silane Oil layer on top of water, no solids.

I Diphenyl dicthoky silane. Liquids drops on bottom of water, no

solids. I

this step was to assureuniformity of wetting and will not 5 treating the strata and other surfaces in the well may,

I treating-the underground strata with the silane material a soap or surfactant to flush or wash away the excess trcat and thereby rendering said formation preferentially oil- I permeable rock or sand structure for increasing the flow a a 1 4 The flasks showed evidence of being water repellent, thusindicating that hydrolysis had taken place.

Conclusion- I Hydrolysis of diphenyl diethdxy silane, trimethyl" ethoxy stlane, and diethyl diethoxy silaneresulted in evidence of solids being formed inthe tests.

mixtures containing only liquid products. There was no While .the treated sand used in'the laboratory tests was 4 1 i first dried using applied or external heat, as h'ereinbefone pointed out. prior to being placed in the glasstubes,

be necessary inactual field operations. Rather as here." inbefore indicated; the solvent-silane: solution used in after allowing sufficient time for the chemical reaction" of the slime material with the rock or sand and like material in the well, be flushed or "displaced directly with the water or other fluidsubsequently' introduced or .other- 'wise.conducted past thetreat'ed surfaces.

Where the water-repellent surfaces which result from are rendered preferentially oil-wettable without actually being oil-wet, it 'will ordinarily be unnecessary to use ing fluid. However, should .oil contamination occur for, some reason, such as during the-subsequent operation of the well, an aqueous soap or surfactant solution mayad- 'vantageously be used in washing away the oil to. restore the water-repellency of the treated surface. This may be '2' v treated. surfaces, such as during'the course of subsequently operating the well as a water disposal or injection well. While the invention has been described herein with particular reference to certain details thereof, it is understood that thcse are by way of example, the scope of the invention being best defined in the appended claims.

What is claimed is: 1. A method of treating non-oil-bearing 'watenwet earthen formations for intreasing the flow rate of water thcrcthrough, comprising the steps .of: (a) injecting into said formationa well treating solu-fltion, said solution consisting essentially of: v

(l) ,a treating agent, whichjdoesnot form a precipitate upon hydrolysis with water,- selected from the group consisting of the organohalogensilanes, the organosilane esters, and mixtures thereof, and I v (2) a water soluble anhydrous solvent which is substantially non-reactive with said treating agent;

wettable; and

(b) flowing water through the treated formationat a' rate greater than that possible throughan untreated i formation'of like composition and under like eondi tions. J 2. The method recited in claim 2, wherein 'said treat- Y ing agent is amyltrichlorosilane.

.3. The method recited in claim I. whereinsaid solvent wisselccted from the group consisting of-iso-propyl alcohol,-

I acetone, formamide, and glacial acetic acid.

4'. The m ethod'recite'din claim 1, wherein said solvent 5 is selected from the group consisting of alcohols, ketones,.

amides, and anhydrous organic acids.

done, asdesired; to facilitate the flowing of water past the i 5. A method of treating. a non-oilrbearingwater-wet M rate of water therethrough, comprising the steps of:

ta) injecting into said structure a solution oia water f soluble anhydrous solvent and a treating agent, substantially non-reactive therewith; which does not form v a precipitate upon hydrolysis with water, selected 4 I .rom the group consisting of the alkylchlo'rosilams,

thealkenylchlorosilanes, the arylchlorosilanes, the

alkylarylchlorosil ancs, the alkylor-g anosilane esters,

4 6. A method of treating water disposal and water injec tionfwell's to renderwater-wet strata therein preferentially 10 oiI-wettableto thereby increase the'fiow of water there- 1 through, comprising the steps of:

ta) introducing into the well-a solution of a water solu ble anhydrous solvent and a treating agent, substantially non-reactive therewith, which does not form a precipitate upon hydrolysis with water, selected from the group consisting of the alkylchlorosilanes, the

alkenylch'lorosilanes, the a-rylchlorosilanes the alkyl- I arylchlorosilanes, the alkylorganosilane esters, the

ters, the alkylarylorganosilane esters, and mixtures thereof; (b) causing said solution to contact a section of the well strata to be treated, thereby rendering such said section preferentially oil-wettable;

(c) the'reafter displacing from the treated section any remaining portion of said solution; and,

(d) fiowing'wat erythrough the treated strata at a rate greater thanthat possible through an unt'reated strata of like composition and under like conditions.

7. A method of treating non-oil-bearing water-wet earthen formations in water disposal wells, water injection wells and water producing wells for increasing the flow of water therethrough, comprising the steps of:

(21) introducing a blanketi'ng fluid into the'well;-

(b) introducing a treating fluid into the well immediately behind said bl'anketing fluid, said treating fluid consistin g essentially of:

(l) a liquid treating agent, which does not form a precipitate upon hydrolysis with .water, selected I from the group consisting of the organoha-logensilanes, and mixtures thereof;- and (2) a water soluble anhydrous solvent which is I substantially iner'twith said treating agent; and,

' from water and other contaminating substances-which may be encountered in'the well; and

15 (d) flowing water through the treated formation at a rate greater than that possible through an untreated formation oflike composition and under like conditionsl 8. The method of claim 7, wherein said blan-lr'eting fluid alkenylorganosilane esters, the arylorganosilane esg waiepsoluble Solvent Selected floin h group n ing of alcohols, ketones, amides-and anhydrous organic acids.--

is amyltrichlorosilane.

25, 10. The method of claim 7, wherein said solvent is selected from the group consisting of iso-propyl alcohol, acetone, formamide and giacial acetic acid.

References Cited by the Examiner 30L UNITED STATES PATENTS V 2,265,962 12/1941 Bentet al. -,1-5&.- 42x 2,469,354. 5/1949 Bond' s 166i-9X 2,633,919 4/1953 BaueretaL- 166-42X 2,846,012

CHARLES E. o'coNN eu, Primar -Exa iner; 5 T. A. ZALENSKI, Assistant Eimminer. I 

1. A METHOD OF TREATING NON-OIL-BEARING WATER-WET EARTHEN FORMATIONS FOR INCREASING THE FLOW RATE OF WATER THERETHROUGH, COMPRISING THE STEPS OF: (A) INJECTING INTO SAID FORMATION A WELL TREATING SOLUTION, SAID SOLUTION CONSISTING ESSENTIALLY OF: (1) A TREATING AGENT, WHICH DOES NOT FORM A PRECIPITATE UPON HYDROLYSIS WITH WATER, SELECTED FROM THE GROUP CONSISTING OF THE ORGANOHALOGENSILANES, THE ORGANOSILANE ESTERS, AND MIXTURES THEREOF, AND (2) A WATER, SOLUBLE ANHYDROUS SOLVENT WHICH IS SUBSTANTIALLY NON-REACTIVE WITH SAID TREATING AGENT; AND THEREBY RENDERING SAID FORMATION PREFERENTIALLY OILWETTABLE; AND (B) FOLLOWING WATER THROUGH THE TREATED FORMATION AT A RATE GREATER THAN THAT POSSIBLE THROUGH AN UNTREATED FORMATION OF LIKE COMPOSITION AND UNDER LIKE CONDITIONS. 